1. Field of the Invention
This invention relates to a method of restoring radioactive soil by initial radioactive assay scanning, fluidization separation, selective ion removal, and concentration.
2. Description of the Prior Art
The contamination of soils, ores, or other materials with radioactive species, such as radium, uranium, and thorium, is a common environmental problem. In a great number of cases, the radioactive contamination is not homogeneously distributed through the mass of soil to be treated, also, it is common for the contamination to be present in a particular fraction of the soil, such as the lighter silt, humic, or clay fraction. In some instances the contaminants may be soluble and in other instances insoluble. The location of such materials varies from residential areas, to mining sites, to radioactive material processing facilities. In all cases, it is necessary to remove or clean up the soil or other material. The disposal of contaminated soil is becoming increasingly expensive, and the practice of digging the soil up in one area, only to bury it in another, is becoming less acceptable environmentally.
In instances in the past, some radioactive waste materials were stored in high integrity 55 gallon containers and placed in underground trenches lined with clay. An improvement of this storage method is described in U.S. Pat. No. 4,778,628 (Grant et al.), where the high integrity containers were stored underground in a barrier structure containing layered activated carbon, zeolite, and clay. These types of solutions are not feasible, however, when the volume of soil or other material involved is extremely large. In the case of soil, typical soil removal methods would remove uncontaminated as well as contaminated soil, usually providing a large volume.
U.S. Pat. No. 4,783,253 (Ayres et al.), teaches a method that partly solves hazardous waste separation problems. There, the waste material is placed in an alternative upward flow of fresh, pure water, and the insoluble contaminants present in the heavy fraction of the waste material are gravitationally removed. However, this process which requires a rather complicated reciprocating diaphragm apparatus and a significant difference in specific gravity between the contaminated and uncontaminated fractions, is primarily limited to high density contamination, and is limited to insoluble contaminants that won't dissolve into the water stream and be washed out of the top of the water column.
What is needed is a simplified method of treating large volumes of materials, for example, up to 9,000 kilograms per hour, containing soluble portions of hazardous or radioactive waste within a particular particle size fraction, so as to segregate the clean from the contaminated material and to concentrate the contaminated material. The method should not require large land areas, so that local treatment is a possibility, and the method should not result in waste disposal or hazardous substance problems. It is one of the main objects of this invention to provide such a method.